Japan should spend ¥10 trillion ($99.83 billion) on fiscal stimulus both in fiscal 2017 and 2018 to offset the economy's lack of demand and eliminate the risk of deflation, an adviser to Prime Minister Shinzo Abe said.

Abe has already compiled a stimulus package for the current fiscal year with ¥7.5 trillion in spending, but the government needs to spend more and do so quickly to boost demand, Abe adviser Satoshi Fujii said Tuesday in an interview.

"We need to spend ¥10 trillion next fiscal year and another ¥10 trillion the following fiscal year to eliminate the deflationary gap," he said.